REFERENCE TO RELATED APPLICATION
This application claims benefit under 35 U.S.C. § 119(a) to Application No. 201910486111.0, filed with the State Intellectual Property Office of the People's Republic of China on Jun. 5, 2019, hereby incorporated herein by reference in its entirety.
BACKGROUND
FIG. 1 illustrates a diagram showing relationships between battery temperature and over-voltage threshold VOV, and between battery temperature and over-current threshold IOC, in a conventional battery protection system. The over-voltage threshold VOV and the over-current threshold IOC are used to protect a rechargeable battery in the battery protection system. For example, during a charging process of the battery, if a battery voltage of the battery is greater than the over-voltage threshold VOV, then the battery voltage is considered too high, and the battery protection system terminates the charging of the battery. Similarly, if a charging current of the battery is greater than the over-current threshold IOC, then the charging current is considered too large, and the battery protection system terminates the charging of the battery. As a result, the battery protection system can protect the battery from over-voltage and/or over-current conditions. As shown in FIG. 1, if the battery temperature is less than TC (e.g., 0° C.), then the battery temperature is considered too low; if the battery temperature is greater than TH (e.g., 40° C., 41° C., 45° C., or the like), then the battery temperature is considered too high. In both situations, the battery protection system prohibits the charger (not shown) from charging the battery. If the battery temperature is between TC and TH, then the battery temperature is considered normal, and the battery protection system allows the charger to charge the battery and sets the over-voltage threshold VOV and the over-current threshold IOC to VTH and ITH, respectively.
However, the conventional battery protection system of FIG. 1 decides whether to charge the battery simply by determining whether the battery temperature is too low or too high. When the battery temperature is considered normal, the conventional battery protection system sets a single over-voltage threshold and a single over-current threshold to protect the battery. This conventional battery protection system may not be able to provide reliable protection for the battery. In addition, deciding whether to charge the battery based on only a single over-voltage threshold and a single over-current threshold may reduce the charging efficiency of the battery, because batteries in different applications may have different temperature characteristics. In other words, in some practical situations, the maximum safe charging power of a battery can change if the battery temperature changes. For example, in a laptop, if a battery has a temperature ranged from 10° C. to 45° C., then the battery can be charged normally, and the battery's over-voltage threshold can be set to a higher level (e.g., 4.25V). If the battery temperature is ranged from 0° C. to 10° C., then the battery can still be allowed to be charged, and its over-voltage threshold is lower (e.g., 4.2V). However, the conventional battery protection system provides a single over-voltage threshold to protect the battery when it is determined that the battery is allowed to be charged, e.g., the battery temperature is within a chargeable temperature range. If the chargeable temperature range is set to be larger, e.g., 0° C. to 45° C., and the over-voltage threshold is set to be higher, e.g., 4.25V, then the battery is not reliably protected when the battery temperature is in the range between 0° C. to 10° C.; if the chargeable temperature range is set to be larger, e.g., 0° C. to 45° C., and the over-voltage threshold is set to be lower, e.g., 4.2V, then when the battery temperature is in the range from 10° C. to 45° C., the charging efficiency of the battery is over-limited and cannot be maximized; and if the chargeable temperature range is set to be smaller, e.g., 10° C. to 45° C., and the over-voltage threshold is set to be higher, e.g., 4.25V, then when the battery temperature is in the range from 0° C. to 10° C., the battery is not charged although the battery is allowed to be charged, which reduces the charging efficiency of the battery. Thus, the conventional battery protection system may not be able to provide reliable protection to the battery in the laptop, and/or may lower the charging efficiency of the battery.
SUMMARY
In embodiments, a threshold setting circuit includes a temperature reference multiplexer, a temperature comparison circuit, and a threshold multiplexer. The temperature reference multiplexer outputs a reference signal of a set of reference signals. The temperature comparison circuit compares a signal indicative of a temperature of a battery with the reference signals output from the temperature reference multiplexer to generate a set of result signals. The threshold multiplexer selects one or more protection thresholds from a set of protection thresholds according to the result signals. The one or more protection thresholds are used to determine whether the battery is in an abnormal condition.
BRIEF DESCRIPTION OF THE DRAWINGS
Features and advantages of embodiments of the claimed subject matter will become apparent as the following detailed description proceeds, and upon reference to the drawings, wherein like numerals depict like parts, and in which:
FIG. 1 illustrates a diagram of relationships between battery temperature and over-voltage threshold, and between battery temperature and over-current threshold, in a conventional battery protection system.
FIG. 2 illustrates a block diagram of an example of a battery protection system, in an embodiment of the present invention.
FIG. 3 illustrates a block diagram of an example of a battery protection system that includes a threshold setting circuit, in an embodiment of the present invention.
FIG. 4 illustrates a diagram of an example of a time sequence for setting a protection threshold, in an embodiment of the present invention.
FIG. 5 illustrates a diagram of relationships between battery temperature and over-voltage threshold, and between battery temperature and over-current threshold in an example of a battery protection system, in an embodiment of the present invention.
FIG. 6 illustrates waveforms for examples of signals, in a threshold setting circuit, that change as a battery temperature changes, in an embodiment of the present invention.
FIG. 7 illustrates a block diagram of an example of a battery protection system that includes a threshold setting circuit, in an embodiment of the present invention.
FIG. 8 illustrates a diagram of relationships between battery temperature and over-voltage threshold, and between battery temperature and over-current threshold, in an example of a battery protection system in an embodiment of the present invention.
FIG. 9 illustrates an example of a method for protecting a battery, in an embodiment of the present invention.
DETAILED DESCRIPTION
Reference will now be made in detail to the embodiments of the present invention. While the invention will be described in conjunction with these embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention.
Embodiments of the present invention provide a battery protection system with a protection threshold setting function. In embodiments, a threshold setting circuit sets a protection threshold (e.g., including an over-voltage threshold and/or an over-current threshold) for protecting the battery according to a temperature range that the battery is in. As a result, the battery is reliably protected in different temperature ranges, and the charging efficiency of the battery is improved.
FIG. 2 illustrates a block diagram of an example of a battery protection system 226, in an embodiment of the present invention. As shown in FIG. 2, the battery protection system 226 is coupled to a battery 222, and provides protection for the battery 222. The battery 222 can include one or more rechargeable battery cells Cell1-Celln (n is a natural number). The rechargeable battery cells can include, but are not limited to, lithium-ion batteries. The battery protection system 226 uses a temperature sensor 202 (e.g., including a thermistor with a negative temperature coefficient), to determine which temperature range the battery 222 is in, and sets a protection threshold to a value corresponding to the temperature range. The protection threshold can be an over-voltage threshold VOV of the battery cells Cell1-Celln or an over-current threshold boy of the battery 222. The over-voltage threshold VOV is used to determine whether voltages VCELL1, VCELL2, . . . , VCELLn of the battery cells Cell1-Celln are within a safe range. If a battery cell's voltage is greater than the over-voltage threshold VOV, then the battery cell's voltage is considered to be too high, and the battery protection system 226 prohibits/stops charging of the battery 222. Similarly, the over-current threshold IOV is used to determine whether a current IBAT (e.g., a charging current) of the battery 222 is within a safe range. If the battery current IBAT is greater than the over-current threshold IOC, then the battery current IBAT is considered to be too large, and the battery protection system 226 prohibits/stops charging of the battery 222.
More specifically, the battery protection system 226 includes a threshold setting circuit and a protection circuit. The threshold setting circuit can determine which temperature range the battery 222 is in, and set a protection threshold based on the temperature range. The protection circuit compares the protection threshold with a battery parameter (e.g., a battery cell voltage or a battery current) to determine whether the battery 222 is in an abnormal condition (e.g., an over-voltage condition or an over-current condition). If it is determined that the battery 222 is in an abnormal condition, then the battery protection system 226 protects the battery 222 by, e.g., stopping the charging of the battery 222. For example, the battery protection system 226 can turn off a charging switch (not shown) that is used to charge the battery 222. More specifically, in an embodiment, a charging switch (not shown) is coupled between the battery 222 and a power input terminal that is used to receive a charging current from a charger (not shown). When the charging switch is on, a charging current from the charger can flow through the charging switch to charge the battery 222. When the charging switch is off, the charging current is disabled. If it is determined that the battery 222 is in an abnormal condition, then the battery protection system 226 can protect the battery 222 by turning off the charging switch. In an embodiment, the charging switch can include a metal-oxide-semiconductor field-effect transistor (MOSFET). The battery protection system 226 can generate a protection signal, e.g., a signal SOV or SOC mentioned below, to control a gate terminal of the MOSFET, thereby turning on or off the MOSFET. However, the invention is not so limited.
FIG. 3 illustrates a block diagram of an example of a battery protection system 226A that includes a threshold setting circuit and a protection circuit, in an embodiment of the present invention. FIG. 3 is described in combination with FIG. 2. As shown in FIG. 3, the battery protection system 226A includes a threshold setting circuit 328 and a protection circuit 330. The threshold setting circuit 328 includes a temperature sensor 202, a temperature reference multiplexer 304, a temperature comparison circuit 306, a logic circuit 320, a threshold multiplexer 308, and a clock generator 318. The protection circuit 330 includes a cell voltage multiplexer 310, a current sensor 316, and an abnormality detection circuit. The abnormality detection circuit includes an over-voltage comparator 312 and can also include an over-current comparator 314.
In an embodiment, the temperature reference multiplexer 304 outputs a reference signal VTREF of a set of reference signals sequentially in a preset order, as described below. In the example of FIG. 3, the set of reference signals includes voltage references VTTC, VTC, VTH, and VTTH, respectively indicative of (or corresponding to) temperature values TTC, TC, TH, and TTH; however, the invention is not limited to four temperature values. The relationship between the temperature values TTC, TC, TH and TTH is as follows: TTC<TC<TH<TTH. In an embodiment, the temperature value TTC means “too cold”, the temperature value TC means “cold”, the temperature value TH means “hot”, and the temperature value TTH means “too hot.” In an embodiment, the voltage references VTTC, VTC, VTH, and VTTH are provided by a thermistor 202 with a negative temperature coefficient. Thus, the relationship between the voltage references VTTC, VTC, VTH, and VTTH is as follows: VTTC>VTC>VTH>VTTH. In an embodiment, the temperature reference multiplexer 304 outputs the reference signals VTTC, VTC, VTH, and VTTH sequentially in a preset order. For example, the preset order of outputting the reference signals can be VTTC, VTC, VTH, and VTTH. For another example, the preset order can be VTTH, VTH, VTC, and VTTC. For yet another example, the preset order can be VTTC, VTTH, VTC, and VTH. However, the invention is not limited to these examples.
The temperature comparison circuit 306 compares a sensing signal VTBAT (e.g., a voltage signal from the thermistor 202) that is indicative of the temperature TBAT of the battery 222 with the reference signals VTREF (e.g., including VTTC, VTC, VTH, and VTTH) output from the temperature reference multiplexer 304, and generates a set of result signals SCTL to indicate a temperature range that the battery 222 is in. The result signals SCTL can include a set of digital signals. In the example of FIG. 3, the positive input terminal of the temperature comparison circuit 306 receives the reference signal VTREF, and the negative input terminal of the temperature comparison circuit 306 receives the temperature sensing signal VTBAT. Thus, if the battery temperature TBAT is greater than the temperature TREF indicated by the reference signal VTREF, then the temperature sensing signal VTBAT is less than the reference signal VTREF, and the temperature comparison circuit 306 outputs a digital signal “1” (e.g., a logic-high signal); or if the battery temperature TBAT is lower than the temperature TREF indicated by the reference signal VTREF, then the temperature sensing signal VTBAT is greater than the reference signal VTREF, and the temperature comparison circuit 306 outputs a digital signal “0” (e.g., a logic-low signal). The temperature comparison circuit 306 compares the sensing signal VTBAT with the reference signals VTTC, VTC, VTH, and VTTH, sequentially, thereby generating a set of result signals SCTL (e.g., digital signals 1000, 1100, or the like) to indicate a temperature range that the battery 222 is in. Taking FIG. 3 as an example, if the result signals SCTL include digital signals 0000, then it indicates that the battery temperature TBAT is less than TTC; if the result signals SCTL include digital signals 1000, then it indicates that the battery temperature TBAT is in the range from TTC to TC; if the result signals SCTL include digital signals 1100, then it indicates that the battery temperature TBAT is in the range from TC to TH; if the result signals SCTL include digital signals 1110, then it indicates that the battery temperature TBAT is in the range from TH to TTH; or if the result signals SCTL include digital signals 1111, then it indicates that the battery temperature TBAT is greater than TTH.
The logic circuit 320 receives the result signals SCTL in series and converts the result signals SCTL to a selection signal SSEL that controls the threshold multiplexer 308. By way of example, the logic circuit 320 receives the result signals SCTL (e.g., including a digital signal string of bits) in series, and converts the digital signal string SCTL to a parallel digital signal SSEL or to another type of selection signal SSEL. Under the control of the selection signal SSEL, the threshold multiplexer 308 selects one or more protection thresholds from a set of protection thresholds according to the result signals SCTL. The one or more protection thresholds are used to determine whether the battery 222 is in an abnormal condition. In an embodiment, the set of protection thresholds includes multiple over-voltage thresholds V1, V2, V3, and V4. Each over-voltage threshold corresponds to one or more temperature ranges of a set of temperature ranges, and is used to determine whether a battery cell in the battery 222 is in an over-voltage condition. More specifically, the protection threshold selected by the threshold multiplexer 308 includes an over-voltage threshold VOV (e.g., V1, V2, V3, or V4) of a battery cell in the battery 222 when the battery 222 is in a temperature range determined by the result signals SCTL. In the example of FIG. 3, the over-voltage threshold V1corresponds to a temperature range from TTC to TC; the over-voltage threshold V2 corresponds to a temperature range from TC to TH; the over-voltage threshold V3 corresponds to a temperature range from TH to TTH; and the over-voltage threshold V4 corresponds to a temperature range below TTC and a temperature range above TTH. In an embodiment, the cell voltage multiplexer 310 outputs a cell voltage VCELL of a battery cell in the battery 222. If the battery cell voltage VCELL is greater than the threshold VOV, it indicates that the battery cell is in an over-voltage condition. In another embodiment, the cell voltage multiplexer 310 outputs a signal indicative of a battery cell voltage VCELL (e.g., proportional to the battery cell voltage VCELL), and the threshold multiplexer 308 outputs a threshold signal VOV indicative of an over-voltage threshold of the battery cell (e.g., proportional to the over-voltage threshold). If the signal output from the cell voltage multiplexer 310 is greater than the threshold VOV, it indicates that the battery cell is in an over-voltage condition.
In an embodiment, the set of protection thresholds also includes multiple over-current thresholds I1, I2, I3, and I4. Each over-current threshold corresponds to one or more temperature ranges of a set of temperature ranges, and is used to determine whether the battery 222 is in an over-current condition. More specifically, the protection threshold selected by the control threshold multiplexer 308 can include an over-current threshold IOC (e.g., I1, I2, I3, or I4) of the battery 222 when the battery 222 is in a temperature range determined by the result signals SCTL. In the example of FIG. 3, the over-current threshold I1 corresponds to the temperature range from TTC to TC; the over-current threshold I2 corresponds to the temperature range from TC to TH; the over-current threshold I3 corresponds to the temperature range from TH to TTH; and the over-current threshold I4 corresponds to a temperature range below TTC and a temperature range above TTH. In an embodiment, a signal VIBAT provided from the current sensor 316 is a voltage signal indicative of (e.g., proportional to) the battery current IBAT. In an embodiment, the threshold multiplexer 308 receives voltage signals VI1, VI2, VI3, and VI4, and outputs a voltage signal VIOC according to a temperature range determined by the result signals SCTL. The voltage signals VI1, VI2, VI3, and VI4 are respectively indicative of (e.g., proportional to) the over-current thresholds I1, I2, I3, and I4, and the voltage signal VIOC is indicative of (e.g., proportional to) the over-current threshold IOC. If the battery current IBAT is greater than the over-current threshold IOC (e.g., the signal VIBAT provided from the current sensor 316 is greater than the voltage signal VIOC), then it indicates that the battery 222 is in an over-current condition. However, the present invention is so limited. In another embodiment, the signal output by the current sensor 316 may be another type of signal, e.g., a current signal I′BAT, indicative of the battery current IBAT. The threshold multiplexer 308 can receive current signals that have current levels proportional to I1, I2, I3, and I4, and can then output, according to the result signals SCTl, a current signal that has a current level proportional to the current threshold IOC. If the current signal I′BAT output from the current sensor 316 is greater than the current signal output from the threshold multiplexer 308, it indicates that the battery 222 is in an over-current condition.
Additionally, the abnormality detection circuit in the protection circuit 330 can receive a protection threshold (e.g., an over-voltage threshold or an over-current threshold) output from the threshold multiplexer 308, and compare the protection threshold and a battery parameter (e.g., a battery cell voltage or a battery current) to generate a comparison result. The comparison result indicates whether the battery is in an abnormal condition. For example, the abnormality detection circuit includes an over-voltage comparator 312. The over-voltage comparator 312 compares a battery cell voltage with an over-voltage threshold, e.g., by comparing a signal VCELL that is output from the cell voltage multiplexer 310 with a signal VOV that is output from the threshold multiplexer 308, to generate a protection signal SOV. If a battery cell in the battery 222 has a voltage greater than the over-voltage threshold, then the protection signal SOV notifies the battery protection system to protect the battery 222, e.g., by turning off a charging switch that is used to charge the battery 222. The abnormality detection circuit can further include an over-current comparator 314. The over-current comparator 314 compares a battery current IBAT with an over-current threshold IOV, e.g., by comparing a signal VIBAT provided by the current sensor 316 with a signal VIOC that is output from the threshold multiplexer 308, to generate a protection signal SOC. If the battery current IBAT of the battery 222 is greater than the over-current threshold IOV, then the protection signal SOC notifies the battery protection system 226 to protect the battery 222, e.g., by turning off the charging switch.
FIG. 4 illustrates a diagram of an example of a time sequence for setting a protection threshold, in an embodiment of the present invention. FIG. 4 is described in combination with FIG. 2 and FIG. 3. In the example of FIG. 4, the threshold setting circuit 328 periodically detects the battery temperature and sets/adjusts one or more protection thresholds (e.g., including an over-voltage threshold VOV and/or an over-current threshold IOC). For example, during time t0 and time t1, the threshold setting circuit 328 receives a sensing signal VTBAT, indicative of the temperature of the battery 222, from the temperature sensor 202 to determine which temperature range the battery 222 is in, and sets a protection threshold according to the temperature range (e.g., by selecting an over-voltage threshold VOV that corresponds to the temperature range from the over-voltage thresholds V1, V2, V3, and V4, and/or by selecting an over-current threshold IOC that corresponds to the temperature range from the over-current thresholds I1, I2, I3, and I4). After the protection threshold is set, the threshold setting circuit 328 enters an idle mode for the time period between time t1 and time t2. In the idle mode, the threshold setting circuit 328 does not check the battery temperature and does not adjust the protection threshold, thereby reducing the power consumption of the battery protection system. When the threshold setting circuit 328 is in the idle mode, the protection circuit 330 compares battery parameters (e.g., including battery cell voltages VCELL1, VCELL2. . . and VCELLn, and/or a battery current IBAT) with corresponding protection thresholds (e.g., including an over-voltage threshold VOV and/or an over-current threshold IOC) to generate protection signals (e.g., SOV and SOC) to protect the battery 222. As shown in FIG. 4, from time t2 to t3, the threshold setting circuit 328 repeats the detection process for the battery temperature and the adjustment process for the protection threshold, and then enters the idle mode during time t3 and time t4. Thus, the threshold setting circuit 328 can periodically perform battery temperature detection and protection threshold adjustment. In an embodiment, since the battery temperature does not change abruptly, the duty cycle of the battery temperature detection and protection threshold adjustment (e.g., the ratio of the time interval from t0 to t1 to the time interval from t0 to t2) can be set to be relatively small to further reduce the power consumption of the battery protection system.
FIG. 5 illustrates a diagram showing relationships between battery temperature and over-voltage threshold VOV, and between battery temperature and over-current threshold IOC (e.g., represented by VIOC), in an example of a battery protection system, in an embodiment of the present invention. In an embodiment, the relationship diagram shown in FIG. 5 is suitable for, but not limited to, a situation when a laptop's battery is being charged. FIG. 5 is described in combination with FIG. 2, FIG. 3, and FIG. 4.
In the example of FIG. 5, if the battery temperature TBAT is lower than the TTC, then the result signals SCTL include digital signals 0000, the over-current threshold IOC is set to I4 (e.g., the voltage signal VIOC is set to VI4), and the over-voltage threshold VOV is set to V4. In an embodiment, the current value I4 can be, but is not limited to, zero amperes. The voltage value V4 can be, but is not limited to, zero volts. If the battery temperature TBAT is in the range from TTC to TC, then the result signals SCTL include digital signals 1000, the over-current threshold IOC is set to I1 (e.g., the voltage signal VIOC is set to VI1), and the over-voltage threshold VOV is set to V1. If the battery temperature TBAT is in the range from TC to TH, then the result signals SCTL include digital signals 1100, the over-current threshold IOC is set to I2 (e.g., the voltage signal VIOC is set to VI2), and the over-voltage threshold VOV is set to V2. If the battery temperature TBAT is in the range from TH to TTH, then the result signals SCTL include digital signals 1110, the over-current threshold IOC is set to I3 (e.g., the voltage signal VIOC is set to VI3), and the over-voltage threshold VOV is set to V3. If the battery temperature TBAT is higher than TTH,then the result signals SCTL include digital signals 1111, the over-current threshold IOC is set to I4 (e.g., the voltage signal VIOC is set to VI4), and the over-voltage threshold VOV is set to V4.
More specifically, in the example of FIG. 5, if the battery temperature is in the range from TC to TH, then the battery temperature can be considered to be in a normal temperature range, and the battery 222 can work in a normal charging mode. In the normal charging mode, the upper limit V2 of the battery cell voltages VCELL1, VCELL2, . . . VCELLn can be relatively high (e.g., approximately equal to the full charge voltage of the battery cell), and the upper limit I2 of the charging current IBAT of the battery 222 (e.g., represented by VI2) can also be relatively large. If the battery temperature is too low (e.g., lower than TTC), or if the battery temperature is too high (e.g., higher than TTH), then the battery 222 can be considered unsuitable for charging. Thus, the upper limit V4 of the battery cell voltage and the upper limit I4 of the charging current (e.g., represented by VI4) are relatively small. If the battery temperature is in the range from TTC to TC, then it can indicate that the battery temperature is relatively low, but the battery can still be charged. Thus, the upper limit V1 of the battery cell voltage is greater than V4 and less than V2 (V4<V1<V2), and the upper limit I1 of the charging current is greater than I4 and less than I2 (e.g., VI4<VI1<VI2). If the battery temperature is in the range from TH to TTH, then it can indicate that the battery temperature is relatively high, but the battery can still be charged. Thus, the upper limit V3 of the battery cell voltage is greater than V4 and less than V2 (V4<V3<V2), and the upper limit of the charging current I3 is greater than I4 and less than I2 (e.g., VI4<VI3<VI2).
FIG. 6 illustrates waveforms for examples of signals, in the threshold setting circuit 328, that change as a battery temperature changes, in an embodiment of the present invention. The signals include VIOC, VOV, SCTL, and VTBAT, where VIOC represents an over-current threshold selected by the threshold multiplexer 308, VOV represents an over-voltage threshold selected by the threshold multiplexer 308, SCTL represents a set of result signals (e.g., including a set of digital signals) output from the temperature comparison circuit 306, and VTBAT represents a sense voltage on the temperature sensor 202. FIG. 6 is described in combination with FIG. 2, FIG. 3, FIG. 4 and FIG. 5.
As shown in the waveforms 602 and 610, between time tA and time tB, the battery is hot (e.g., the battery temperature TBAT is relative high but not too high), and the temperature sensing signal VTBAT is less than the reference VTH and greater than the reference VTTH. Thus, as shown in the waveform 604, the result signals SCTL output from the temperature comparison circuit 306 include digital signals 1110. After time tB, as shown in the waveforms 606 and 608, the threshold multiplexer 308 sets the over-voltage threshold VOV and the over-current threshold VIOC to the threshold V3 and the threshold VI3 respectively, where the thresholds V3 and VI3 correspond to the digital signals 1110. From time tC to time tD, the battery temperature TBAT has dropped to a normal temperature range, and the temperature sensing signal VTBAT is less than the reference VTC and greater than the reference VtH. Thus, as shown in the waveform 604, the result signals SCTL, output from the temperature comparison circuit 306 include digital signals 1100. After time tD, as shown in the waveforms 606 and 608, the threshold multiplexer 308 sets the over-voltage threshold VOV and the over-current threshold VIOC to the threshold V2 and the threshold VI2 respectively, where the thresholds V2 and VI2 correspond to the digital signals 1100.
In the embodiments of FIG. 3, FIG. 5, and FIG. 6, the threshold setting circuit 328 compares the battery temperature TBAT with four temperature values TTC, TC, TH, and TTH, e.g., by comparing the temperature sensing signal VTBAT with the voltage references VTTC, VTC, VTH, and VTTH, and selects, according to results of the comparison, a threshold VOV from four over-voltage thresholds V1, V2, V3, and V4, and a threshold VIOC from four over-current thresholds VI1, VI2, VI3, and VI4. However, the present invention is not so limited. In other words, the number of temperature references, the number of the over-voltage thresholds, and the number of the over-current thresholds are not limited to four.
By way of example, a battery protection system 226B that includes a threshold setting circuit 728 is illustrated in FIG. 7, in another embodiment of the present invention. FIG. 7 is described in combination with FIG. 2, FIG. 3, FIG. 4, FIG. 5, and FIG. 6. As shown in FIG. 7, the threshold setting circuit 728 can compare the battery temperature TBAT and N temperature references TR1, TR2, . . . , TRN (N is a natural number), thereby selecting a corresponding over-voltage threshold VOV from X over-voltage thresholds V′1, V′2, . . . , V′X (X is a natural number), and selecting a corresponding over-current threshold VIOC from Y over-current thresholds VI′1, VI′1, . . . , VI′1 (Y is a natural number). The numbers N, X, and Y can be the same or different from one another.
FIG. 8 illustrates a diagram showing relationships between battery temperature and over-voltage threshold VOV, and between battery temperature and over-current threshold IOC (e.g., represented by VIOC), in an example of a battery protection system, in an embodiment of the present invention. In an embodiment, the relationship diagram shown in FIG. 8 is suitable for, but not limited to, a situation when a signal battery cell (e.g., a battery in a mobile phone) is being charged. FIG. 8 is described in combination with FIG. 7.
In the example of FIG. 8, the number N of the temperature references is five, the number X of the over-voltage thresholds is four, and the number Y of the over-current thresholds is three. If the battery temperature is lower than TR1 or higher than TR5, then the battery is considered unsuitable for charging. Thus, the over-voltage threshold V′X and the over-current threshold VI′Y are set to be relatively small (e.g., zero volts and zero amperes, respectively). The over-voltage thresholds V′1, V′2, and V′3 correspond to the temperature range from TR1 to TR3, the temperature range from TR3 to TR4, and the temperature range from TR4 to TR5, respectively. The over-current thresholds VI′1and VI′2 correspond to the temperature range from TR1 to TR2, and the temperature range from TR2 to TR5, respectively. Thus, the threshold setting circuit 728 can set an appropriate protection threshold by determining which temperature range the battery is in.
FIG. 9 illustrates an example of a method for protecting a battery, in an embodiment of the present invention. FIG. 9 is described in combination with FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, FIG. 7, and FIG. 8. Although specific steps are disclosed in FIG. 9, such steps are examples for illustrative purposes. That is, embodiments according to the present invention are well suited to performing various other steps or variations of the steps recited in FIG. 9.
At step 902, a temperature reference multiplexer (e.g., the multiplexer 304 in FIG. 3 or the multiplexer 704 in FIG. 7) sequentially outputs a set of reference signals VTREF (e.g., including the voltage references VTTC, VTC, VTH, and VTTH corresponding to the temperature values TTC, TC, TH, and TTH in FIG. 3, or the voltage references VTR1, VTR2. . . VTRN corresponding to the temperature values TR1, TR2. . . TRN in FIG. 7).
At step 904, a temperature comparison circuit 306 compares a sensing signal VTBAT indicative of a temperature TBAT of the battery 222 with the reference signals VTREF output from the temperature reference multiplexer to generate a set of result signals (e.g., SCTL in FIG. 3 or S′CTL in FIG. 7).
In step 906, a threshold multiplexer (e.g., the multiplexer 308 in FIG. 3 or the multiplexer 708 in FIG. 7) selects one or more protection thresholds from a set of protection thresholds according to the set of result signals (e.g., SCTL, or S′CTL). In the example of FIG. 3, the set of protection thresholds includes over-voltage thresholds V1, V2, V3, and V4, and/or over-current thresholds VI1, VI2, VI3, and VI4. In the example of FIG. 7, the set of protection thresholds includes over-voltage thresholds V′1, V′2, . . . , V′X, and/or over-current thresholds VI′1, VI′2, . . . , VI′Y.
At step 908, a protection circuit 330 determines whether the battery 222 is in an abnormal condition according to the selected one or more protection thresholds. Taking FIG. 3 as an example, if a battery cell's voltage VCELL in the battery 222 is greater than the over-voltage threshold VOV selected by the threshold multiplexer 308, then that battery cell is considered to be in an over-voltage condition. If a charging current IBAT of the battery 222 is greater than the over-current threshold IOC selected by the threshold multiplexer 308 (e.g., represented by the voltage signal VIOC), then the battery 222 is considered to be in an over-current condition.
In summary, embodiments according to the present invention provide battery protection systems with a protection threshold setting or adjusting function. A threshold setting circuit in the battery protection system sequentially receives a set of reference signals indicative of a set of temperature values, and compares the received reference signals with a sensing signal indicative of a battery temperature to generate a set of result signals. Because the comparison process is relatively simple, it can be implemented by a comparison circuit that is relatively small and relatively inexpensive, thereby reducing the size of printed circuit board of the battery protection system and also reducing the cost of the system. In addition, the threshold setting circuit determines which temperature range the battery is in according to the result signals, and selects one or more protection thresholds from a set of protection thresholds (e.g., including a set of over-voltage thresholds and/or a set of over-current thresholds) corresponding to that temperature range. The battery protection system provides protection to the battery based on the selected protection threshold. Thus, compared to a conventional battery protection system, the battery protection system in an embodiment of the present invention can provide more reliable protection to the battery in different temperature ranges, and can improve the charging efficiency of the battery.
While the foregoing description and drawings represent embodiments of the present invention, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope of the principles of the present invention as defined in the accompanying claims. One skilled in the art will appreciate that the invention may be used with many modifications of form, structure, arrangement, proportions, materials, elements, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims and their legal equivalents, and not limited to the foregoing description.
Patent Application
20200389041
